Connector system with precision alignment

ABSTRACT

A system includes mateable connectors (12, 14) with mateable optic fiber termini, which provides for precision alignment of the termini and which facilitates installation of an insert whose front end must be of rectangular shape. Two mating sets of optic fiber termini (30, 32) are precisely aligned by a pair of pin-receiving alignment holes (44, 46) in one connector and a pair of pins (40, 42) projecting from the other connector, wherein a first (40) of the alignment pins is precisely cylindrical and fits closely in the first hole, and a second (42) of the pins is also precisely cylindrical but fits into a hole (46) that is elongated in a direction toward and away from the first hole. A front portion (110) of an insert is of largely rectangular cross-section, while the rear portion (112) of the insert is of largely circular cross-section to enable retention by a circular retainer clip (120) and to provide threads (122) for threading into a backshell.

CROSS REFERENCE

This is a division of U.S. patent application Ser. No. 08/744,127 filedNov. 5, 1996, now U.S. Pat. No. 5,778,121.

BACKGROUND OF THE INVENTION

There have been attempts to incorporate fiber optic termini in standardrack and panel electrical contact connectors. In such connectors,largely elongated rectangular inserts are mounted in elongated housings,and a number of such connectors may be arranged in a row. When adaptingthis type of connector to optic termini wherein the tips of a pair ofmating optical fibers must precisely abut one another, high precision isrequired to assure that the tips of the fibers are in line and thefibers extend parallel. A connector system which assured reliable matingof optical fiber termini, especially in standard rack and panelconnector housings, would be of value.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, a connectorand connector system are provided, which include fiber optic termini,which assure precise alignment of mating termini and which facilitateretention and coupling to an optic fiber insert whose front end must berectangular. A second connector has a housing with a pair of alignmentbores, while a first connector has a pair of projecting alignment pinsfor reception in the bores. A first pin is of cylindrical shape and isvery closely received in a first cylindrical bore, while the second pinis cylindrical but is received in a bore that is elongated in adirection radial to the first bore. This results in the second pin beingprecisely angularly positioned with respect to the axis of the firstpin, but not radially positioned with respect to the axis of the firstpin.

An insert for one connector has a rectangular front portion for closelyfitting in a rectangular bore of the corresponding housing. However, therear of the insert is of circular cross-sections, to enable use of acircular retention clip and to provide a thread for engagement with abackshell.

The novel features of the invention are set forth with particularity inthe appended claims. The invention will be best understood from thefollowing description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded isometric view of a connector system of thepresent invention, showing receptacle and plug connectors thereof.

FIG. 2 is a sectional view of the system of FIG. 1, showing theconnectors approaching each other, but not yet close enough to fullymate.

FIG. 3 is a front elevation view of the first, or receptacle connectorof FIG. 1.

FIG. 4 is a side elevation view of the connector of FIG. 3.

FIG. 5 is a rear elevation view of the connector of FIG. 3.

FIG. 6 is a front elevation view of the second, or plug connector ofFIG. 1.

FIG. 7 is a side elevation view of the connector of FIG. 6.

FIG. 8 is a rear elevation view of the connector of FIG. 6.

FIG. 9 is a partial sectional view of a pair of fully mated connectorsof another embodiment of the invention.

FIG. 10 is a rear isometric view of the fiber optic insert of thesecond, or plug connector of FIG. 1.

FIG. 11 is a partial front elevation view of the plug connector of FIG.6, and including sectional views of alignment pins inserted intoalignment bores of the plug connector.

FIG. 11A is an enlarged view of a portion of FIG. 11.

FIG. 12 is a view similar to that of FIG. 11, but showing anotherembodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a connector system 10 which includes a first orreceptacle connector 12 and a second or plug connector 14 that can mateby moving the connectors together along their axes 16, 18. Each of theaxes extend in corresponding forward and rearward directions Fr, Rr forreceptacle connector and Fp, Rp for the plug connector. Each connectoris elongated in a longitudinal direction M and is shorter in aperpendicular lateral direction L, with directions M, L beingperpendicular to the forward and rearward directions for each connector.The first connector 12 has an electrical contact insert 20 that includesa plurality of electrical pin contacts 22. The pin contacts mate withsocket contacts 24 of an electrical contact insert 26 of the secondconnector. The first connector also includes a pair of connectorelements in the form of butt-joint optical termini 30 that can mate withcorresponding termini 32 of a fiber optic insert 34 of the secondconnector. When electrical contacts such as 22, 24 mate, it is necessarythat they be aligned with moderate accuracy, such as with the axes ofthe corresponding pin and socket contacts being aligned within a fewthousandths inch and within a few degrees. However, when the optictermini are to be mated, they must be aligned with higher precision,such as being coaxial within about one-thousandth inch and with anangular misalignment within about one degree. A pair of alignment pins40, 42 of the first connector are received in a pair of alignment bores44, 46 of the second connector, to assure such precision alignment.

FIG. 2 shows the two connectors 12, 14 in the process of mating, butrequiring movement of several millimeters towards each other for finalor complete mating. The first connector includes a metal housing 50 thathas been machined with a recess 52 to hold the first electrical contactinsert 20. The first electrical contact insert includes a rigidinsulative body 56 within which the electrical contacts 22 are mounted,and front and rear rubber like grommets 60, 62 for sealing out moisture.Wire conductors 65 are connected to rear ends of the contacts. Thesecond electrical insert 26, of the second connector 14, is of similarconstruction and is held in a corresponding metal housing 70 of thesecond connector. Each first fiber optic terminal 30 lies in an aperture64 bored in the metal housing 50 of the first connector. Each of thesecond fiber optic terminals 32 of the second connector lie in anaperture 66 formed in a metal frame 70, or insert housing, of the secondfiber optic insert 34.

Each of the two fiber optic termini 30 of the first connector includes aferrule 72 that projects from a front face 74 of the first housing, withan optical fiber 76 lying within the ferrule. Each mating fiber opticterminus 32 of the second connector includes mating front endscomprising a ferrule 80 that lies within a precision ceramic sleeve 82that also can receive the ferrule 72 of the first connector. Theterminus 32 has a rear end 84 that is coupled to an optic cable 86 thatincludes a fiber. The second ferrule 80 can move rearwardly in directionRr under biasing of a spring, to assure that the extreme tips of theferrules and of the optical fibers therein abut one another. It is wellknown that efficient transfer of light for butt-joint optic fibercoupling requires that the tips of the ferrules and fibers lie preciselyconcentric and with the ferrules and fibers oriented to extend preciselyparallel to each other.

Precision alignment is assured by the alignment pins 40, 42 of the firstconnector that project into the alignment bores 44, 46 of the secondconnector. The metal housing 50 of the first connector has a pair ofholes 90, 92 that receive the alignment pins 40, 42 in interference fittherein. The alignment bores 44, 46 of the second connector receive thepins in precision sliding fit therein. In one example, the first bore 44has an inside diameter A of 0.2500 inch, while the corresponding pin 40has an outside diameter B of 0.2495 inch. This results in a differencein diameters of 0.5 mil (one mil equals one thousandth inch) and aclearance around the pin 40 of 0.25 mil. The second alignment pin 42 andsecond bore 46 could be similarly constructed, except that this wouldrequire the distance C between the two bores and between the two pins tobe held accurate within a few ten thousandths inch. Positioning thealignment bores 44, 46 and pins 40, 42 with their distances C held tothis accuracy, would result in high cost. Applicant avoids this byforming the second bore 46 with a larger dimension E in a directionradial to the first bore 44 (i.e. radial to the axis 100 of the firstbore).

FIG. 11 shows the two bores 44, 46 with the two pins 40, 42 lyingtherein, with FIG. 11A showing the region of the second bore and secondpin. The first bore and first pin are centered on a first axis 100. Thesecond pin 42 has a cylindrical portion lying in the second bore 46. Thesecond bore 46 has the same width A in a lateral direction L as thefirst bore; the second bore width A is only a few ten thousandths inchgreater than the diameter B of the second pin 42. However, the height Eof the second bore (in a direction radial to axis 100) is much greaterthan the diameter B of the second pin. In one example, the height E ofthe second bore is 0.270 inch, leaving a clearance F above and below thepin of about 0.010 inch. The clearance F is preferably more than 0.001inch. As a result, the function of the second bore 46 is to fix thelateral position (L) of the second pin, and to fix the angular position(in the circumferential direction D) of the second pin 42 about thefirst axis 100 to a small fraction of one degree. In a connector systemthat applicant designed, the distance C is 0.79 inch, so the alignmentpins lie close to the optic termini. A lateral clearance G of 0.25 milresults in any pivoting of the pin 42 about the axis 100 at the centerof the pin 40 being limited to about ten arc minutes. The difference 2Gin width will almost always be less than 2 mils. No contact is desiredbetween the second pin 42 and the longitudinally (M in FIG. 11A)opposite sides 101, 103 of the second bore 46. FIG. 11A shows that thepin 42 is of circular cross-section while the bore 46 is elongated in alongitudinal direction M. The circumferentially (with respect to axis100) opposite sides 105,106 of the second pin 42 lie very close to thecircumferentially opposite sides 107, 108 of the second bore 46.

The two bores 44, 46 are preferably formed on a milling machine whereina rotating cutter is moved into the frame 70 and out again to form thefirst circular bore 44, the cutter then moved to the position of thesecond bore 46. The cutter is then moved into the frame 70 to form ahole, and with the rotating cutter still in the hole, the cutter ismoved in a direction R that is radial to the first axis 100 (with Rbeing parallel to M), to form a bore that is not precisely circular, butis elongated in a direction radial to the first axis 100.

FIG. 12 shows another construction, wherein the first pin 40 and firstbore 44 are of the same construction as in FIG. 11. However, the secondbore 46A is cylindrical, and therefore of circular cross-sections, butthe second alignment pin 42A is not circular. The second alignment pin42A is radially flattened in that it is formed with "flats" at 102, 104so it has a small thickness in the radial or longitudinal directions R,M. With the thickness P of the second pin being no more than aboutone-third the original diameter B, the radial clearance (between pin 42Aand bore 46A) in the longitudinal direction M is about three times theclearance in the lateral direction L. It is noted that while twoalignment pins (e.g. 40, 42 in FIG. 2) are shown projecting from oneconnector to slideably fit into two bores in the other connector, it ispossible to provide for only one alignment pin to project from eachconnector and to provide one alignment bore in each connector, with thetwo arrangements (one or two pins on a connector) being the equivalentof each other.

FIG. 10 is a rear isometric view of the second fiber optic insert 34, ofthe second connector. The front portion 110 must be of largelyrectangular cross-section (as viewed along the axis of the connector andaxis 123). Applicant prefers to form the rear portion 112 ofsubstantially circular cross-sections. This has several advantages. Oneadvantage is that this results in a circular retention surface 116. FIG.2 shows that the retention surface 116 lies within a correspondingcylindrical surface 118 formed in the second housing 70, and with aretention clip 120 lying in the thin gap 121 between the retentionsurface 116 and the hole at 118 in the housing. The clip liessubstantially against shoulders of opposite ends of the gap. Suchretention clips 120 are readily available as reliable devices forretaining an insert, while enabling the insert to be readily removed andreplaced by using a tool to cause the clip to release the insert. Suchreliable clips are available only in circular shapes. The circularsectioned rear portion lies on an insert axis 123. A transition location111 (FIG. 10) between circular and rectangular sections lies forward ofthe gap 121.

The rectangular insert front portion 110 has longitudinally spacedopposite ends 125, 127 extending beyond the threaded shank portion 122.The alignment bores 44, 46 extend through these overhanging end portions125, 127. It can be seen that the rear portion 112 of the insert has athread 122, which enables a protective backshell 124 to be readilyattached to the insert by screwing the backshell into place on thethread 122. The round cross-section at the thread enables suchattachment. By applicant providing the fiber optic insert 34 with atransition between the largely rectangular forward portion 110 oflargely rectangular cross-section, and the largely circular rear portion112 of largely circular cross-sections, applicant is able to provide theproper shape at the front of the connector while enhancing retention andconnections at the rear of the insert.

In FIG. 2, it can be seen that applicant forms the first housing withapertures or bores 64 for receiving the fiber optic termini 30, wherethe bores 64 are formed directly in the metal housing 50. It would bepossible to provide an insert similar to the insert 34 for the secondconnector. However, applicant avoids the need for a largeinsert-receiving hole and increases rigidity and reliability, by formingthe optic terminus-receiving bores directly in the metal housing of thefirst connector. The forward portion 130 of each bore is especiallyuseful to fix the orientation and position of the terminus ferrule 72(although the sleeve 82 provides a high precision adjustment).

FIG. 2 shows a cone-shaped rubber seal 140 around each first terminus,for providing a water tight seal with a hole in the second insert. FIG.9 shows another arrangement (as would be seen on lines 9--9 of FIG. 3,but modified), where an O-ring 144 is provided that lies in a groove ofa forwardly-projecting lip 146, to seal to a sleeve-like projection 150.An O-ring provides a more uniform sideward force to the termini ferrulesthat would lie in the bores 64A.

Applicant has designed a connector system of the construction shown inFIGS. 1-8 and 10-11. Each connector had an overall longitudinal length Jof 3.744 inch (FIG. 6), and a lateral width K of 1.200 inch, with thesecond connector having a depth Q (FIG. 7) of 1.185 inch. FIG. 2 isdrawn to show other dimensions accurately proportional to the length anddepth.

Thus, the invention provides a connector system with connectors that canmate and that each has at least one fiber optic terminus that can matewith that of the other connector, which provides precision alignment ofthe fiber optic termini and which provides an insert with a rear portionconstructed to ease retention and connection. A pair of alignment pinsprojecting from one connector are received in a pair of alignment boresin the other connector, with a first pin and bore having precisioncylindrical surfaces that are closely engaged, and with a second pin endbore constructed to precisely fix their circumferential position withrespect to the axis at the first pin bore, but to avoid fixing theirradial positions with respect to the axis of the first pin and bore. Aninsert for one of the connectors has a largely rectangular front portionfor fitting into a correspondingly-shaped cavity formed in the connectorhousing. However, the rear of the insert is constructed to have largelycircular cross-sections, which facilitates the use of a retaining clipand the use of an external thread. One or more bores in a firstconnector for receiving optic fiber termini, are bored directly into themetal housing of the first connector for added precision and durability.The first connector housing has an aperture for receiving an electricalconnector insert that contains electrical connectors, whose positionsare not as critical as required for optic fiber termini.

Although particular embodiments of the invention have been described andillustrated herein, it is recognized that modifications and variationsmay readily occur to those skilled in the art, and consequently, it isintended that the claims be interpreted to cover such modifications andequivalents.

What is claimed is:
 1. A connector system comprising:first and secondconnectors that can mate by moving the connectors together, said secondconnector having first and second alignment bores and said firstconnector having first and second alignment pins for projectingrespectively into said first and second bores; said first bore and saidfirst pin each having interfitting cylindrical portions lying on a firstaxis to precisely fix the relative positions of said connectors at saidfirst pin and first bore, in directions perpendicular to said firstaxis, said second bore and said second pin each being spaced in a radialdirection from said first axis; said second bore and said second pineach having a pair of circumferentially opposite sides that arecircumferentially spaced apart with respect to said first axis withsmall circumferential clearances (G) between them, but said second boreand said second pin have radially opposite ends that are radially spacedwith respect to said first axis and that have clearances (F) betweenthem that are each a plurality of times greater than each of saidcircumferential clearances, so said second bore and pin do not fix theirradial positions with respect to said first axis.
 2. The connectorsystem described in claim 1 wherein:said circumferential clearance (G)is no more than a few ten thousandths inch, while said clearances (F) atsaid radially opposite ends are more than one thousandth inch.
 3. Aconnector comprising:a housing having an axis extending in front andrear axial directions and having an axially extending through aperture,said aperture having walls forming an aperture front end portion oflargely rectangular cross-section and an aperture rear end portion; aninsert having a substantially rectangular insert front portion that liesclosely in said aperture front end portion and having an insert rearportion, said insert having at least one connector element with a frontmating end and a rear end; said insert rear portion and said aperturerear portion forming a clip-holding gap between them, with said insertrear portion forming a rearwardly-facing shoulder at the front of saidgap and said aperture forming a forwardly-facing shoulder at the rear ofsaid gap; a retainer clip lying in said gap and positioned to engagesaid shoulders, with said clip being circular, and with said apertureand said insert having a rectangle-to-circle transition forward of saidgap, so the walls of said aperture and of said insert are of circularcross-sections at said gap.
 4. The connector described in claim 3wherein:said insert has an insert axis extending parallel to saidhousing axis, and said insert rear portion includes a threaded shankportion lying on said insert axis rearward of said gap and having athread diameter that is smaller than the outside diameter of said insertat said gap; said rectangular insert front portion has opposite endsthat each projects radial to said insert axis by a distance greater thanthe radius of said threaded shank portion to provide an overhangingrectangular end portion that lies beyond said shank as viewed along saidinsert axis; a pair of alignment pin-receiving holes each extendingparallel to said insert axis and projecting through one of saidoverhanging rectangle end portions.
 5. A connector systemcomprising:first and second connectors that can mate by moving theconnectors together, said second connector having first and secondalignment bores and said first connector having first and secondalignment pins for projecting respectively into said first and secondbores; said first bore and said first pin each having interfittingcylindrical portions lying on a first axis to precisely fix the relativepositions of said connectors at said first pin and first bore, indirections perpendicular to said first axis, said second bore and saidsecond pin each being spaced in a radial direction from said first axis;said second bore and said second pin each having a pair ofcircumferentially opposite sides that are circumferentially spaced apartwith respect to said first axis with small circumferential clearances(G) between them, but said second bore and said second pin have radiallyopposite ends that are radially spaced with respect to said first axisand that have clearances (F) between them that are each a plurality oftimes greater than each of said circumferential clearances, so saidsecond bore and pin do not fix their radial positions with respect tosaid first axis; said second pin has a cylindrical pin portion lying insaid second bore, but said second bore has a bore portion surroundingsaid pin portion with said bore portion having a greater radial lengthin a direction radial to said first axis than its circumferential widthin a direction that is circumferential to said first axis.
 6. Aconnector system comprising:first and second connectors that can mate bymoving the connectors together, said second connector having first andsecond alignment bores and said first connector having first and secondalignment pins for projecting respectively into said first and secondbores; said first bore and said first pin each having interfittingcylindrical portions lying on a first axis to precisely fix the relativepositions of said connectors at said first pin and first bore, indirections perpendicular to said first axis, said second bore and saidsecond pin each being spaced in a radial direction from said first axis;said second bore and said second pin each having a pair ofcircumferentially opposite sides that are circumferentially spaced apartwith respect to said first axis with small circumferential clearances(G) between them, but said second bore and said second pin have radiallyopposite ends that are radially spaced with respect to said first axisand that have clearances (F) between them that are each a plurality oftimes greater than each of said circumferential clearances, so saidsecond bore and pin do not fix their radial positions with respect tosaid first axis; said second pin has a flattened pin portion lying insaid second bore and said second bore has a cylindrical bore portionthat surrounds said flattened pin portion, but while said flattened pinportion has a circumferential width substantially equal to thecircumferential width of said cylindrical bore portion to leave a verysmall circumferential clearance thereat, said flattened pin portion hasa radial length that is less than its circumferential width to leave amuch larger radial clearance thereat that is a plurality of timesgreater than said circumferential clearance.